The preparation of fluconazole (IV) by alternative processes has been described in British Patent No. 2,099,818.
A first process involves reacting a compound of the formula V: ##STR2## where Q is a facile leaving group, with 1,2,4-triazole wherein Q is Cl or Br.
A second possible process is reacting an oxirane of the formula VI: ##STR3## with 1,2,4-triazole.
In both cases, these reactions are not regiospecific and two isomers are observed in the product mixture. In British Patent 2,099,818 it is stated that, "the product will generally be contaminated with the isomer in which one of the triazole rings is attached to the adjacent CH.sub.2 via the 4-position." Therefore, the process of British Patent 2,099,818 discloses the need for column chromatography to isolate the desired product from the side product iso-fluconazole.
This lack of regiospecifity in the fluconazole process, as described in British Patent 2,099,818, leads to the following disadvantages: low overall yield; requirement for column chromatography; lack of suitability for usual industrial production conditions, and final product contamination with iso-fluconazole.
In contradistinction to the teachings of said British patent, there has now been surprisingly discovered, according to the present invention, a regiospecific process for the preparation of 1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol derivatives of the general formulas I and Ia: ##STR4## wherein: R is alkyl, cycloalkyl, aryl or aralkyl optionally substituted by one or more same or different halogen groups; and
X is the anion of a strong acid; PA1 R.sub.1 is hydroxy, halogeno, alkyl, cycloalkyl, aryl, aralkyl or a heterocyclic group, each optionally substituted or unsubstituted. PA1 R.sub.1 is hydroxy, halogeno, alkyl, cycloalkyl, aryl, aralkyl or a heterocyclic group, each optionally substituted or unsubstituted, and PA1 X is the anion of a strong acid;
comprising reacting an oxirane acid salt of the general formula II: ##STR5## wherein R and X are as defined above; or reacting an oxirane of the general formula II': ##STR6## wherein R and X are as defined above, under acidic conditions, with 4H-4-amino-1,2,4-triazole of the formula III: ##STR7## and optionally deaminating a compound of the formula Ia to form a compound of formula I.
In preferred embodiments of the present invention the process will be carried out with an oxirane acid salt of the general formula II as defined above rather than with an oxirane of the general formula II' in the presence of acid.
Preferably X is the anion of a strong acid selected from the group consisting of chloride, sulphate, p-toluenesulphonate and methanesulphonate.
In the process of the present invention the compounds of formula I as defined above are prepared, inter alia, by the deamination of the intermediate compounds of formula Ia as defined above, which intermediate compounds are novel per se and which intermediate compounds have therefore also not been previously taught or suggested for use in the preparation of the compounds of formula I. These novel intermediates can be isolated, if desired, or reacted in situ, as described and exemplified herein, for the preparation of the compounds of formula I.
As will be noted, in the process of the present invention there is used a 4-amino-1,2,4-triazole of formula III, in which the possibility of 4-alkylation is blocked by an amino group.
Bret A. Astleford, et al, J. Org. Chem., Vol. 54, No. 3, p. 731 (1989), describes a synthesis of 1-(2,4-dichlorophenyl)-2-(1H-1,2,4-triazyl-1-yl)ethanone of the formula VII: ##STR8## in a regiospecific procedure using 4H-4-amino-1,2,4-triazole (III) in the condensation with 2-chloro-2',4'-dichloroacetophenone of the formula VIII: ##STR9## resulting in the isomerically pure hydrochloric salt of IX: ##STR10## which is then deaminated with sodium nitrate to give the 1-2,4-dichlorophenyl-1-2-(1H-1,2,4-triazol-1-yl)ethanone of formula VII.
As will be noted, however, said Astleford et al reference does not teach the reaction of a 4-amino-1,2,4-triazole with an oxirane and, as shown in comparative Example A hereinafter, when such a reaction is attempted under the conditions described therein, a complex product mixture is obtained in which fluconazole is only a minor component.
Likewise, when the reaction conditions disclosed in the Example D of the British Patent 2,099,818 are attempted using 4-amino-1,2,4-triazole instead of triazole as described in comparative Example B hereinafter, the desired product was not significantly present in the reaction mixture.
The reactions described in the prior art Astleford, et al. and British Patent 2,099,818 between triazole or aminotriazole and the chloride, or between triazole and the oxirane specify basic reaction conditions. The novel reaction of the present invention between aminotriazole and the oxirane surprisingly requires acidic conditions.
In especially preferred embodiments, said anion of the strong acid is methanesulphonate or p-toluenesulphonate.
The process of the present invention preferably comprises deamination of a compound of formula Ia, to form a compound of formula I and in especially preferred embodiments of the present invention, there is provided a regiospecific process wherein R is 2,4-difluorophenyl, whereby the process provides fluconazole of formula IV.
As will be realized, once fluconazole has been prepared according to the novel process of the present invention, it, or a pharmaceutically acceptable salt thereof, can be used for the preparation of pharmaceutical compositions as taught, e.g., in British Patent 2,099,818, the teachings of which are incorporated herein by reference.
Thus, as known and taught in said patent, the preferred pharmaceutically acceptable salts are the acid addition salts. Pharmaceutically acceptable acid addition salts of the compounds of the formula I are those formed from strong acids, which form non-toxic acid addition salts containing a pharmaceutically-acceptable anion, such as hydrochloride, hydrobromide and sulphate.
The salts may be obtained by conventional procedures, e.g., by mixing solutions containing equimolar amounts of the free base and desired acid, and the required salt is collected by filtration, if insoluble, or by evaporation of the solvent.
Thus the present invention also provides a compound of formula I, or a pharmaceutically acceptable salt thereof, whenever prepared by the process of the present invention, for use in treating fungal infections in humans.
Furthermore, the general principle of the reaction in the process of the present invention between the oxirane or oxirane acid salt and a 4H-4-amino-1,2,4-triazole may be utilized in similar instances where a substituted oxirane or oxirane acid salt is desired to be reacted with a 1,2,4-triazole, i.e., instances where the oxirane is of the formula XI: ##STR11## or oxirane acid salt is of the formula XIa: ##STR12## wherein: R is as defined above, and
Thus, the present invention also relates to a regiospecific process for the preparation of 1-(1,2,4-triazol-1-yl)-propan-2-ol derivatives of the general formulas XII and XIIa: ##STR13## wherein: R is as defined above;
comprising reacting an oxirane acid salt of general formula XIa: ##STR14## wherein R, R.sub.1 and X are as defined above; or reacting an oxirane of the general formula XI: ##STR15## wherein R, R.sub.1 and X are as defined above, under acidic conditions, with 4H-4-amino-1,2,4-triazole of the formula III: ##STR16## and optionally deaminating a compound of the formula Ia to form a compound of formula I.
An example of such a reaction, where the above process may be of use, is the one between (R)-(-)-2-(2,4-difluorophenyl)-2,3-epoxropanol and 1,2,4-triazole described in Drugs of the Future, Vol. 18 pp 424-427 (1993), wherein the 1,2,4-triazole may be replaced by a 4H-4-amino-1,2,4-triazole and the conditions outlined in the present application applied, to yield the desired product.
For human use, the anti-fungal compound of the formula I (or salt thereof) can be administered alone, but will generally be administered in admixture with a pharmaceutical carrier selected with regard to the intended route of administration and standard pharmaceutical practice. For example, it may be administered orally in the form of a tablet containing such excipients as starch or lactose, or in a capsule or ovule, either alone or in admixture with excipients, or in the form of an elixir or suspension containing a flavoring or coloring agent. It may be injected parenterally, for example, intravenously, intramuscularly or subcutaneously. For parenteral administration, it is best used in the form of a sterile aqueous solution which may contain other substances, for example, enough salts or glucose to make the solution isotonic.
For oral and parenteral administration to human patients, it is expected that the daily dosage level of the anti-fungal compound of the formula I will be from 0.1 to 5 mg/kg (in divided doses) when administered by either the oral or parenteral route. Thus tablets or capsules of the compounds can be expected to contain from 5 mg to 0.5 g of active compound for administration singly, or two or more at a time, as appropriate. The physician, in any event, will determine the actual dosage which will be most suitable for an individual patient and it will vary with the age, weight and response of the particular patient. The above dosages are exemplary of the average case. There can, of course, be individual instances where higher or lower dosage ranges are merited, and such are within the scope of this invention.
Alternatively, the anti-fungal compound of formula may be administered in the form of a suppository or pessary, or it may be applied topically in the form of a lotion, solution, ointment or dusting powder. For example, it may be incorporated into a ointment consisting of an aqueous emulsion of polyethylene glycols or liquid paraffin, or it may be incorporated, at a concentration, with such stabilizers and preservatives as may be required.
The process of the present invention is preferably carried out in alcohols, water, dimethylsulphoxide, dimethylformamide, acetonitrile, etc., at 50.degree. to 100.degree. C., preferably in boiling 2-propanol followed by deamination with sodium nitrite.
As indicated, R is preferably a halogen-substituted aryl group, and when R is 2,4-difluorophenyl, the product obtained is fluconazole (IV).
According to the method of this invention, IV is isolated in a substantially pure state, without the need for column chromatography. In contrast to British Patent No. 2,099,818, no isomeric side product is observed, even in the crude reaction mixture. The yield of fluconazole is also superior to that disclosed in British Patent 2,099,818.